Soil Biodiversity

Considerations for the use of soil ecological classification and assessment concepts in soil protection

In comparison with other environmental compartments, the protection of soil was identified relatively late as an important issue. Even later, policy makers and the general public considered the ecological functions of the soil. However, recently, the central role of these functions, as well as the importance of the soil organism community, has become obvious in several countries in Europe and in the European Union itself. In this contribution, basic considerations referring to use of ecological endpoints for the classification and assessment of soils are discussed. The article begins with two goals of protection: to protect soil so that it can function and to protect soil as a habitat for organisms necessary for these functions. Afterward, the quality of soil from is discussed from a biological point of view. Finally, on the basis of experience from limnology and botany, recommendations are made for monitoring programs. In other articles of this series, details of the entire approach to ecological classification and assessment are outlined.

Ecosystem carbon loss with woody plant invasion of grasslands

The invasion of woody vegetation into deserts, grasslands and savannas is generally thought to lead to an increase in the amount of carbon stored in those ecosystems. For this reason, shrub and forest expansion (for example, into grasslands) is also suggested to be a substantial, if uncertain, component of the terrestrial carbon sink. Here we investigate woody plant invasion along a precipitation gradient (200 to 1,100 mm yr(-1)) by comparing carbon and nitrogen budgets and soil delta(13)C profiles between six pairs of adjacent grasslands, in which one of each pair was invaded by woody species 30 to 100 years ago. We found a clear negative relationship between precipitation and changes in soil organic carbon and nitrogen content when grasslands were invaded by woody vegetation, with drier sites gaining, and wetter sites losing, soil organic carbon. Losses of soil organic carbon at the wetter sites were substantial enough to offset increases in plant biomass carbon, suggesting that current land-based assessments may overestimate carbon sinks. Assessments relying on carbon stored from woody plant invasions to balance emissions may therefore be incorrect.